This chapter explores the complexities and practical strategies of conducting mental health assessments literally on the streets where people sleeping unsheltered live. Recognizing that trauma and mistrust of psychiatric systems are common among people sleeping rough, the chapter emphasizes building trust before making a diagnosis. It introduces the Rapid Street Psych Assessment (RSPA), a tool designed to support quick, symptom-focused evaluations suited to chaotic, outdoor settings. The RSPA prioritizes ruling out psychosis and mania before assessing for PTSD and depression, enabling clinicians to safely prescribe medications with limited time and information. The chapter offers concrete guidance on distinguishing between symptoms of psychiatric disorders—such as psychosis, PTSD, ADHD, and bipolar disorder—while accounting for overlapping symptoms and substance use effects. It stresses the value of “good-enough” diagnoses that support timely treatment, rather than exact DSM-5 labels, particularly in environments where long assessments can hinder care. The chapter also provides tools and conversational techniques to navigate complex patient presentations, ensuring clinicians can respond compassionately and effectively. Overall, it is a practical guide to ethical, trauma-informed, and efficient diagnostic practices in unsheltered care settings.